PubMed Health⌕ Search

Biomedical subjects

R Bauer

Publications and source records attributed to R Bauer.

At least 73 records · Page 4Linked to original sources
PubMed1994

Autoantibodies against ganglioside GM3 represent a portion of anti-lymphocyte antibodies in AIDS patients.

In this study we analysed the relationship between anti-lymphocytic ganglioside antibodies and anti-lymphocyte antibodies in AIDS patients. Anti-lymphocytic ganglioside antibodies were detected by thin layer chromatography (TLC) immunostaining; three colour flow cytometry was used to analyse circulating antibodies against different lymphocyte subsets. Anti-lymphocytic ganglioside antibodies were detected in 23 out of 49 AIDS patients sera (46.9%). All positive sera reacted selectively with the GM3 comigrating band from AIDS lymphocytes. Twenty two out of the 23 anti-lymphocytic GM3 positive sera also had antibodies against CD4+T cells, versus 17/26 anti-GM3 negative. Furthermore, patients with lymphocytic GM3 antibodies showed a significantly higher antibody reactivity against CD4+ T cells than patients in which these antibodies were not detected. The absorption tests revealed that preincubation of positive sera with GM3 was followed by a decrease in the reaction with target lymphocytes. These findings suggest that anti-GM3 antibodies are a portion, but not the majority, of antibodies reacting with CD4+ T cells.

Acquired Immunodeficiency Syndrome↗
PubMed1994

[Molecular cloning of a new AP-2 transcription factor, AP-2beta, and its function in cell differentiation].

Transcription factor AP-2 has been previously shown to play an important function in embryonal development and cell differentiation. We have investigated the possibility that AP-2 function in embryonic development is exerted by a multigene family of AP-2 related transcription factors. Here we describe the molecular cloning of such an AP-2 related gene, AP-2 beta, and prove that it encodes for a functional transcription factor. In situ hybridizations of murine embryo sections revealed a temporally restricted and tissue-specific expression pattern that indicates a function of AP-2 beta in the development of the midbrain in the differentiation of sensory neurons for taste, olfaction and palpation.

Animals↗
PubMed1994

Forms of physiological aliasing within the heart rate fluctuations by higher frequent respiratory movements.

In adult conscious rabbits, the respiratory frequency (RF) is almost always higher than half the heart rate (HR) Thus, no "classical" respiratory sinus arrhythmia occurred. But now, slow HR fluctuations, which were not synchronous to the respiratory rhythm but effected by it, occurred systematically. By cholinergic blockade, these slow HR fluctuations could be essentially reduced but not completely abolished. Up to now, this phenomenon was not be taken into account in the analysis of HR fluctuations. Thus misinterpretations are inevitable. During general anaesthesia, the RF decrease up to 2 RF < HR, and now classical respiratory sinus arrhythmia occurred which also could be essentially reduced but not completely abolished by vagal blockade. The possibilities of calculation of such slow HR fluctuations were shown, as those during 1/2 HR < RF < 3/2 HR and RF > 3/2 HR.

Acid-Base Equilibrium↗
PubMed1994

Alpha 1-antitrypsin Pittsburgh (Met358-->Arg) inhibits the contact pathway of intrinsic coagulation and alters the release of human neutrophil elastase during simulated extracorporeal circulation.

Cardiopulmonary bypass prolongs bleeding time, increases postoperative blood loss, and triggers activation of plasma proteolytic enzyme systems and blood cells referred to as the "whole body inflammatory response". Contact of blood with synthetic surfaces leads to qualitative and quantitative alterations in platelets, neutrophils, contact and complement systems. Contact and complement pathway proteins both induce neutrophil activation. alpha 1-antitrypsin Pittsburgh (Met358-->Arg), a mutant of alpha 1-antitrypsin, is a potent inhibitor of plasma kallikrein and thrombin. We investigated whether this recombinant mutant protein inhibited platelet activation, as well as contact and/or complement-induced neutrophil activation during simulated extracorporeal circulation. Arg358 alpha 1-antitrypsin did not prevent the 34% drop in platelet count at 5 min of recirculation, did not block the 50% decrease in ADP-induced platelet aggregation at 120 min of recirculation, nor inhibit the release of 6.06 +/- 1.07 micrograms/ml beta-thromboglobulin at 120 min of recirculation suggesting that the inhibitor had little effect on platelet activation. However, Arg358 alpha 1-antitrypsin totally blocked kallikrein-C1-inhibitor complex formation but not C1-C1-inhibitor complex formation. Most importantly, Arg358 alpha 1-antitrypsin decreased the release of 1.11 +/- 0.16 micrograms/ml human neutrophil elastase by 43%. The attenuation of neutrophil activation in the absence of an effect on complement activation via the classical pathway, supports the concept that kallikrein is a major mediator of neutrophil degranulation during cardiopulmonary bypass.

Arginine↗
PubMed1994

Extraordinary efficacy of 16 alpha-gitoxin, an ultra-short acting semi-synthetic digitalis glycoside.

The positive inotropic effect of 16 alpha-gitoxin was studied in 52 female and male healthy volunteers between the ages of 21 and 27 years and a body weight between 55 and 76 kg after the single i.v. injection or oral administration in doses between 2.5 and 15 mg. The inotropic effect was evaluated by the use of the systolic time intervals (left ventricular ejection time, LVET, and electromechanic systole, QS2) and by the QT-Interval of the ECG. The glycoside plasma level was measured simultaneously to the pharmacodynamic parameters by a radioimmunoassay, 16 alpha-gitoxin abbreviated dose-dependently the STI (LVET and QS2) for 30 (i.v.) or 15 ms (per os) and the QT interval for 35 ms. A mean plasma concentration of 401 ng/ml was measured 15 minutes after the i.v. injection of 5 mg and a mean plasma level of 402 ng/ml was measured 1 hour after the oral intake of 10 mg 16 alpha-gitoxin as an aqueous-ethanolic solution. The shortening of the STI-values and of the QT-interval correlated with the administered glycoside dose and with the AUC0-6-value. The AUC-values increased linearly with the administered dose. The ratio of the AUC0-6-values after i.v. or oral administration of 7.5 mg 16 alpha-gitoxin amounted to 0.673. Doses of 16 alpha-gitoxin which induce a maximum abbreviation of STI or QT did neither provoke a distinct decrease in heart rate nor cardiac disturbances. Sixteen-alpha-gitoxin develops a positive inotropic effect within a few minutes after i.v. injection and also after oral intake.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1993

The influence of ionic strength and pH on the aggregation properties of zinc-free insulin studied by static and dynamic laser light scattering.

The aggregation properties of zinc-free insulin have been studied using static and dynamic light scattering. The aggregation has been investigated as a function of three parameters, the concentration of sodium chloride (in the range 10-100 mM), the pH value (in the range pH 7.5-10.5), and the insulin concentration (1.8-13.4 mg/mL). The measured homodyne autocorrelation function was used to determine the apparent mean hydrodynamic diameter as well as the apparent weight-averaged molar mass of the insulin species in solution. A method of data analysis was employed, which allows the separation of light scattering contributions from the insulin oligomers and from irrelevant macromolecules and possible impurities present in the sample solutions. Also, a simple phenomenological equilibrium model describing the association of oligomers of insulin is presented. One aspect of this model is that it makes it possible to determine weight average molar masses corrected for virial effects on the Rayleigh ratio. This was necessary because virial effects cannot be isolated and corrected for by dilution since this would change the equilibrium distribution of oligomers. The basis of the model is a positive contribution to Gibbs free energy from charge repulsion depending on the protein charge and the number of monomers in the oligomers, and an assumed constant negative contribution to Gibbs free energy arising from either an entropic gain or hydrogen bonding upon association. The equilibrium model gives a good description of both the apparent weight average molar masses and the apparent hydrodynamic diameters, when the effect of the insulin concentration is taken into account by including virial effects arising from charge-charge repulsion (Donnan effect). The result shows that the association of insulin as a function of pH and ionic strength can be described by an effective charge equal to the charge derived from proton titration reduced by the number of sodium ions binding to insulin. At the lowest pH and highest salt concentration (pH 7.5, 100 mM NaCl, 12 mg/mL insulin), the weight average molar mass is close to that of the hexamer, and at the highest pH and lowest salt concentration (pH 10.5, 10 mM NaCl, 1.9 mg/mL), the weight average molar mass is close to that of the monomer. In all cases, however, a distribution of oligomers is present with a relative Gaussian width of about 30%.(ABSTRACT TRUNCATED AT 400 WORDS)

Chemical Phenomena↗
PubMed1993

Functional expression of bacterial beta-glucuronidase and its use as a reporter system in the yeast Yarrowia lipolytica.

The use of beta-glucuronidase (beta-GUS) as a reporter and sensitive detection system for Yarrowia lipolytica was studied. The Escherichia coli gusA gene was expressed under control of the homologous LEU2 promoter in a transcriptional fusion. An NcoI restriction site was introduced at the translational start-ATG, conserving the most favorable context for initiation of translation. The chimeric LEU2'-gusA gene was integrated into the LEU2 locus by homologous recombination. The beta-GUS assay was very sensitive and highly reproducible, using the cytosolic fraction or a total cell extract as the source of enzyme. In a leucine-free medium, beta-GUS activity was at a high, constant level, independent of growth phase. In transformants grown on complete medium, beta-GUS activity was reduced about three-fold, but doubled during logarithmic growth. No intrinsic beta-GUS activity was detectable in untransformed Y. lipolytica and no effect of beta-GUS expression on growth was observed. beta-GUS-producing Y. lipolytica cells could be directly detected on media plates containing X-gluc (5-bromo-4-chloro-3-indolyl-beta-D-glucuronide).

Base Sequence↗
PubMed1993

[Selection--a key concept for the structural and functional self-organization of the brain?].

Starting from well-known concepts and theoretical work in biology and economics, the self-organization of the brain is defined as a three-fold selection process with three different time scales. As a morphogenetic and functional principle, selection operates at a phylogenetic, an ontogenetic, and a cognitive level. Especially the hypothesis of a fast cortical selection extends the explanatory power of this central biological concept to conscious higher brain functions.

Animals↗
PubMed1993

Brain resuscitation by extracorporeal circulation after prolonged cardiac arrest in cats.

OBJECTIVE: Brain reanimation after prolonged ischemia is limited by post-ischemic reperfusion deficits (no-reflow phenomenon). The present study was undertaken to establish whether after 30 min cardiac arrest extracorporeal circulation is able to restore brain reperfusion and to promote functional and metabolic recovery. DESIGN: Adult normothermic cats were submitted to 30 min cardiac arrest by KCl-induced cardioplegia. Resuscitation was carried out by extracorporeal circulation (ECC) until spontaneous heart function returned. The quality of brain recovery was assessed 3 h later by electrophysiological recording and by imaging of the regional distribution of brain energy metabolites. RESULTS: In 6 of 10 cats cardiac sinus rhythm returned after 32 +/- 15 min. In the other 4 cats cardiac function did not return or only intermittently returned during the 3 h observation period. Cerebral blood flow measured by laser Doppler flowmetry returned to 102% +/- 40% of control immediately after the beginning of resuscitation but then gradually declined to 43% +/- 32% after 3 h despite normotensive perfusion. In all cats pupils started to constrict within less than 5 min of recirculation but in 2 animals they secondarily dilated 1.5 and 2 h later, respectively. Spontaneous EEG activity reappeared in 4 of the 6 successfully resuscitated cats after 111 +/- 40 min but failed to recover in the others. Bioluminescent imaging of ATP after 3 h recirculation revealed near-complete depletion throughout the brain in all 4 cats without cardiac recovery. Of the 6 successfully resuscitated cats 5 exhibited patchy areas of low ATP, glucose and pH in 22%-92% of the cross sectional area of brain; in one cat recovery of energy metabolism and acid-base homoeostasis was homogeneous without any focal deficits. The cross sectional area of ATP recovery correlated directly with CBF and hematocrit and inversely with the plasma lactate level. CONCLUSIONS: This study demonstrates for the first time that ECC is able to restore electrophysiological and metabolic brain function after cardiac arrest of as long as 30 min, but recovery is heavily restricted by delayed post-ischemic disturbances of recirculation. Progress in cardiac resuscitation by ECC requires substantial improvement in the efficiency of cerebrovascular reperfusion.

Acid-Base Equilibrium↗
PubMed1993

Different anisotropies for texture and grating stimuli in the visual map of cat striate cortex.

A comparison was made of the directional preferences of cat area 17 cells tested with two different stimuli, gratings and random-dot patterns. Depending on the stimulus, different distributions of direction preferences (anisotropies) were found in the same cells of the central representation of upper layers. With gratings most common preferred directions were vertical and horizontal. With textures, however, horizontal preferred directions were most common. In contrast, lower layer neurons had a bias for vertical preferred directions regardless of the type of stimulus used.

Animals↗
PubMed1993

Effect of culture conditions on IgM antibody structure, pharmacokinetics and activity.

Culture conditions affect the binding activity, charge heterogeneity, conformational stability, glycosylation, and pharmacokinetics of human monoclonal IgM HMAB-10058. The 10058 human/human/murine trioma was grown in serum-free airlift suspension culture, hollow fiber perfusion culture, or in nude mouse ascites. The ascites-produced antibody showed reduced conformational stability, greater charge and glycoform heterogeneity, and a lower average degree of sialylation than the in vitro culture-produced material. Mean residence time after IV injection in rats was approximately 80-fold greater for the ascites culture-produced material, but specific binding activity was less than 5% of that for the airlift-produced material. In vitro culture in serum-supplemented media (in a hollow fiber perfusion reactor or in shake-flasks) resulted in antibody with pharmacokinetics intermediate between the serum-free airlift and ascites-produced materials. Incubation of airlift-produced antibody in ascites fluid also resulted in material with intermediate pharmacokinetics. Conclusions regarding the effect of culture conditions on antibody product cannot be generalized, as in vitro-produced antibody derived from two related cell lines (HMAB-10233 and HMAB-10390) had long mean residence times similar to that of ascites-produced HMAB-10058.

Animals↗
PubMed1993

High frequency (60-90 Hz) oscillations in primary visual cortex of awake monkey.

It has been proposed that synchronized oscillations play a key role in perceptual feature linking and sensory integration. This idea was supported by the discovery of strongly synchronized stimulus-specific oscillations in the visual cortex of anaesthetized cats. The 'synchronization hypothesis' was controversial because in the visual cortex of awake monkeys either only weak or no oscillations were found. We have now recorded high amplitude synchronized oscillation at the level of spike activity and local field potential from the primary visual cortex of an awake monkey. The dominant frequencies (70-80 Hz) were considerably higher than those observed previously in cats and monkeys (30-50 Hz). However, stimulus specificities of the oscillations were comparable to and amplitudes even higher than those in cats.

Animals↗